Studies on the crystal structure of (D-Ala)-B0 porcine insulin at 1.9 A resolution

The crystal structure of (D-Ala)-B0 porcine insulin has been determined, using data to 1.9 A and atomic parameters of 2 Zn porcine insulin as a starting model, and through the use of the difference method and the restrained least square method, to a final R-factor of 0.211 and r.m.s. deviation of 0.057 A for the bond lengths. The electron densities of B0 residues were very clear. Introduction of B0 residues into the molecules had reduced the thermal vibration of the N-terminus of B-chain for both molecules I and II and made the molecules pack closer in the crystal. The obvious differences between the crystal structures of 2 Zn and (D-Ala)-B0 porcine insulin were the conformations of partial polar groups around the possible receptor binding surface and the assembly mode of two helixes of A-chain in molecule I. In the local environment of the N-terminus of B-chain there were great differences between the crystal structures of (D-Ala)-B0 porcine insulin, (Trp)-B1 porcine insulin and Des B1(Phe) bovine insulin. In this paper the structure-immunoactivity relationships of insulin molecule have also been discussed briefly.